A known failure determination device for a current sensor is of a type which determines a failure of the current sensor that detects the current of a battery supplying electric power to an electric load (see, e.g., Patent Document 1). This failure determination device focuses on the fact that, due to the internal resistance of the battery, the battery voltage decreases as the battery current increases. In other words, the device detects the change amount of the battery current when the battery voltage changes by a reference change amount and determines, if the change amount of the battery current is a reference value or lower, that an intermediate fixed failure has occurred in the current sensor because the battery current, which should have changed, has not changed due to a failure of the battery sensor.
Patent Document 1: JP-A-10-253682